Voiding, honey combing and cracks in the material.Low quality concrete areas are detected successfully.With multiple testing paths the area, size and shape of defect is measured.With direct path tests the engineer gets a 2-side access.Complex geometry is tested around corners or beam intersections.Surface-to-surface tests also can be conducted with depth measurements. https://www.rtulgroup.com/how-does-pulse-velocity-test-work-for-structural-concrete-condition-assessment/